This invention relates to a powered system, such as a marine vessel, and, more particularly, to a system and method for providing rechargeable energy on a marine vessel.
Mechanically, two kinds of marine vessels generally exist currently. A first version has a main engine that drives a main propeller, usually a variable pitch propeller, and that also drives a generator. FIG. 1 depicts a block diagram illustrating a prior art two-engine configuration for a marine vessel. Though a single combination of two engines 12, 13 is disclosed, multiple sets of this same configuration are used in some marine vessels. Furthermore, the engines need not be used as sets. For example, two of engine 12 may be used with one of engine 13. Similarly, multiple engines of the same type may be utilized.
A first engine 12 drives a main propeller 14, which may be a fixed pitch propeller or a variable pitch propeller, and where the engine speed may vary. The propeller may be driven through a gear box 11. A second engine 13 drives a generator 16 that produces a fixed voltage and fixed frequency of alternating current (“AC”) power, such as but not limited to 600 volts, 60 Hertz. AC power from the generator 16 is provided to an AC bus distribution unit or station 18. Motors, for example thrust motors 20, may be driven with drives 22 connected to the AC bus distribution unit 18. Other loads 24, such as, but not limited to, winches, hoists, pumps, fans, auxiliary loads, lighting, etc., are also powered from the AC bus distribution unit 18. Power to the AC bus distribution unit 18 may be supplied by other sources, such as, but not limited to, other on-board generators or off-board sources, including port and/or dock stationary generators. Therefore, though one AC bus distribution unit 18 is illustrated, those skilled in the art will readily recognize that a plurality of bus distribution units 18, propellers 14, engines 12, 13, and generators 16 may be utilized.
FIG. 2 depicts a block diagram of another prior art marine system where a single engine 12 drives a propeller 14. In this configuration, engine speed runs at a speed proportional to AC bus frequency and the propeller pitch is controlled. Though only a single engine/propeller combination is illustrated, multiple combinations are typical in marine vessels. A generator 16, driven by the engine 12 and at least one gearbox 11, produces a fixed voltage and a fix frequency AC power, such as but not limited to 600 volts, 60 Hertz. AC power from the generator 16 is provided to an AC bus distribution unit or station 18. Motors, for example thruster motor 20, may be driven with drives 22 connected to the AC bus distribution unit 18. Other loads 24, such as, but not limited to, winches, hoists, pumps, fans, auxiliary loads, lighting, etc., are also powered from the AC bus distribution unit 18. Power to the bus distribution unit 18 may be supplied by other sources, or generators, such as, but not limited to, other on-board generators, off-board sources including dockside and/or port side electrical outlets, and port and/or dock stationary generators. Therefore, though one AC bus distribution unit 18 is illustrated, those skilled in the art will readily recognize that a plurality of bus distribution units 18, engines 12, propellers 14, and generators 16 may be utilized.
FIG. 3 depicts an electrical drive configuration for a marine vessel, according to the prior art. As illustrated, electrical power is provided from the engine 13, through the generator 16, and then to the AC bus distribution unit 18. Electrical power is provided from the AC bus distribution unit 18 to the main motor propeller 14 by way of its drive 15, thrust motor propeller 20 by way of its drive 22, and other loads 24, which are disclosed above. The engine in this configuration typically runs at a constant speed to generate the appropriate frequency for an AC distribution system for the marine vessel.
In each embodiment disclosed above, the engine 12 provides initial power to the marine vessel. Therefore, the engine 12 must be operating to provide power. As marine vessels are currently used, for example when the marine vessel is a tugboat, the prior art mechanical drive and electrical drive configurations disclosed above result in fuel consumption and emissions being produced even while the tugboat is waiting to perform a mission. Owners and operators of marine vessels would benefit from a system and method where emissions are reduced and fuel use is lowered, due to how hybrid energy is provided and used aboard the marine vessel. This is especially desirable when the marine vessel, such as, but not limited to a tugboat, is waiting to assist a larger ship, is stationary, or is handling a light load. Owners and operators also will benefit from having marine vessels that operate quieter when close to shorelines where engine noise is not desired.